The invention relates to coupling devices for tubular railing which are internally expanded to lock the railing sections together.
There are numerous prior art methods for achieving such a coupling, as shown in the following patents:
U.S. Pat. No. 3,514,135 to Cooper PA1 U.S. Pat. No. 2,850,304 to Wagner PA1 U.S. Pat. No. 2,997,317 to Scott PA1 U.S. Pat. No. 4,102,529 to Neblung.
Most of these patents, such as the Cooper and Scott patents, utilize a locking screw which levers the coupling sleeve against itself to expand the sleeve, while in the present invention the wedging means, which expands the sleeve, is drawn to the railing section itself. With the coupling of the present invention, not only does the expanded sleeve provide a friction locking joint against the inside diameter of the rail section, but also the two locking screws in conjunction with the wedge member provide a secondary lap joint for any tensile loadings. The heads of the locking screws are always in a flush position with the rail sections, regardless of the degree of tightening on the wedge member. The wedging member of the present invention includes an indexing groove which assists in aligning and assembling the coupling. The wedging member also includes a tab arrangement on the ends thereof for maintaining the sleeve and wedge member as a unitary structure in the unassembled state.